[Effect of plasmid pIJ350 on genetic stability of antibiotic production by Streptomyces bambergiensis].

It was shown that S. bambergiensis S800 was genetically instable with respect to the property of the antibiotic production (Ant) while in strain S712 of S. bambergiensis this property was stable. Transformation of S. bambergiensis protoplasts with pIJ350 plasmid DNA and analysis of the transformants screening revealed induction of the Ant instability in both the strains. In case of plasmids pVG101 and pIJ943 this effect was not shown. Analysis of the S800 (pIJ350) transformant screening revealed five groups of mutants differing in the antibiotic production level and the presence of pIJ350 plasmid. Restriction analysis of the total DNA of the mutants showed that there were large deletions in the genome of two of them. Retransformation of the mutants with pIJ350 plasmid DNA showed that in all the cases induction of the instability was lacking. The behaviour of the spontaneous mutants Ant- of strain S800 with respect to pIJ350 plasmid was analogous to that of the mutants Ant- from the transformant S800 (pIJ350) screening. A hypothetic model for the determinant incompatibility with pIJ350 plasmid genetically linked to the Ant property in the genome of S. bambergiensis and unstable in strain S800 was proposed.